High emissivity coating compositions and manufacturing processes therefore

ABSTRACT

Titanium dioxide is used as an emissivity enhancer in high emissivity coating compositions. The titanium dioxide increases the emissivity of the high emissivity coating compositions. In certain embodiments, titanium dioxide is recovered from industrial waste sources such as catalyst containing waste streams from olefin polymerization processes or re-based sources. Titanium dioxide emissivity enhancers recovered from industrial waste solution sources contribute favorably to the cost of manufacturing high emissivity coating compositions containing such enhancers.

BACKGROUND

1. Technical Field

The present disclosure relates generally to compositions for highemissivity coatings that can be applied to various types of substrates,and to processes for manufacturing high emissivity coating compositions.More particularly, the present disclosure relates to (1) high emissivitycoating compositions with enhanced strength properties, (2) highemissivity coating compositions in which titanium dioxide (TiO₂) is usedan emissivity enhancing agent; and (3) manufacturing processes forcost-effectively producing high emissivity coating compositions using anindustrial waste source or stream.

2. Description of the Related Art

Increasing demand for energy and rising energy costs throughout theworld have inevitably increased the need for energy users to save orconserve energy, particularly among industrial entities. In manyinstances, industries that use fired heaters or furnaces, such asrefineries and petrochemical complexes, have attempted to maximize firedheater efficiency to thereby reduce fuel consumption. High emissivitycoating technology has become a proven means for various hightemperature applications to effectively increase radiant heat transferand save energy without compromising process reliability and safeoperation.

Emissivity (symbolically represented as c or e) can be broadly definedas the relative ability of a surface to emit energy by radiation. Moreparticularly, emissivity can be defined as the ratio of energy radiatedby a particular material to energy radiated by a blackbody at the sametemperature. Higher emissivity corresponds to an increase in thermalefficiency. An increase in thermal efficiency attributed to highemissivity coatings in high temperature fired heater or furnaceapplications results in an increase in fired heater or furnaceperformance or output and/or a decrease in fuel consumption and overallenergy demand.

The benefits and advantages of high emissivity coatings have led tovarious research and development efforts over the years to improve theperformance of high emissivity coatings. In particular, research hasbeen conducted to develop emissivity coating compositions that includeemissivity enhancing agents (“emissivity agents”) to a) enhanceemissivity values in order to increase radiant heat transfer; b) improvecoating adhesion on substrates; c) extend coating lifetime acrossmultiple high temperature cycles; and d) reduce emissivity agentdegradation.

Currently, several high emissivity coating compositions are commerciallyavailable. Emissivity agents in such compositions can be derived fromvarious sources. One commonly used emissivity agent is silicon carbide(SiC), which can exhibit good emissivity enhancement performance up tomoderate temperatures. However, the use of SiC as an emissivity agent inapplications involving high operating temperatures (e.g., fire heater,furnace, preheater, reformer, other refractory applications, oraerospace applications) can lead to a substantial decrease in emissivityand mechanical strength of the coating composition over time, and hencean overall decrease or degradation in the performance or function of acoating composition relying upon SiC as an emissivity agent.

In NASA Technical Memorandum 130952, entitled “Thermal Degradation Studyof Silicon Carbide Threads Developed for Advanced Flexible ThermalProtection Systems,” published in August 1992, H. K. Tran and P. M.Sawko found that a surface transition of SiC to SiO₂ was observed attemperatures greater than 400° C. The surface transition of SiC to SiO₂was due to temperature induced decomposition of SiC bonds and thesubsequent formation of SiO₂. The decomposition reaction of SiC at hightemperature can be illustrated as follows:

SiC+O₂→SiO₂+CO₂

Such decomposition of SiC can undesirably result in significant materialshrinkage, unintended SiO₂ passivation, and shorter coating compositionlifetime. Accordingly, a need exists for improved emissivity agents forhigh emissivity coating compositions, particularly with respect toimproving emissivity agent performance of emissivity coatings at hightemperatures. Unfortunately, prior research on high emissivity coatingcompositions has failed to adequately consider or recognize that certainsubstances can potentially have a significant impact on enhancingemissivity values.

In addition to the foregoing, although aspects of high emissivitycoating performance are being investigated and improved, existingprocesses for manufacturing high emissivity coating compositions fail toappropriately consider or address certain economic aspects of producingsuch compositions. In particular, while various efforts have been madeto develop high emissivity coatings with better performance, suchefforts have largely ignored or unavoidably increased the cost ofproducing such coating compositions and the end price of high emissivitycoating products. Accordingly, there is a need for preparing,manufacturing, or formulating high emissivity coating compositions in amore cost-effective manner.

BRIEF SUMMARY

Embodiments of the subject matter described in this application aredirected to thermal emissivity coatings that exhibit desirablemechanical strength properties and emissivity over a broad range oftemperatures, (e.g., about 400° C. to about 1300° C. Unlike otheremissivity coatings that exhibit cracking and delamination fromsubstrates to which the coatings are applied, embodiments of the subjectmatter described herein survive repeated temperature cycles from roomtemperature to temperatures typically used in decoking cycles, e.g.,about 1000° C. to about 1600° C. or higher, without cracking ordelamination from underlying substrates. At the same time coatingcompositions in accordance with embodiments described herein exhibitdesirable emissivity, e.g., as high as 0.99.

In one aspect, embodiments described herein are directed to thermalemissivity coatings that include a dry admixture of a set of emissivityagents including titanium dioxide, wherein a weight percentage of thetitanium dioxide is less than approximately 28% by weight of the coatingcomposition and at least approximately 10% by weight of the coatingcomposition, and a set of matrix strength enhancers selected from atleast one of ceramic borides, ceramic carbides, and ceramic nitrides. Insome embodiments of this aspect of the described subject matter thecoating includes less than 30 wt % SiC on a dry basis.

In another aspect, embodiments described herein are directed to methodsof preparing thermal emissivity coating compositions for a substratethat include steps of obtaining titanium dioxide; providing a set ofemissivity agents including the titanium dioxide; providing a set ofmatrix strength enhancers that includes at least one matrix strengthenhancer selected from the group consisting of ceramic borides, ceramiccarbides, and ceramic nitrides; providing a set of fillers, at least onefiller selected from the group consisting of aluminum oxide, silicondioxide, magnesium oxide, calcium oxide, and boron oxide; and combiningthe set of emissivity agents, the set of matrix strength enhancers, andthe set of fillers, wherein the filler comprises about 2 wt % to about60 wt % on a wet basis of the coating composition. In some embodimentsof this aspect of the described subject matter SiC is provided such thatthe coating composition includes less than 30 wt % SiC on a dry basis.

In yet another aspect, disclosed embodiments are directed to methods formodifying thermal emissivity of a substrate using a thermal emissivitycoating composition that includes steps of identifying a targetemissivity level or a target emissivity modification; determining acoating composition titanium dioxide concentration expected to providethe target emissivity level or the target emissivity modification;determining a set of substrate adhesion properties for the coatingcomposition; determining a coating composition SiC concentrationexpected to provide the determined set of substrate adhesion properties;and providing a thermal emissivity coating composition that includes thedetermined titanium dioxide concentration and the determined SiCconcentration. In some embodiments of this aspect of the describedsubject matter, the determined SiC concentration is less than 30 wt %SiC on a dry basis.

In another aspect, the titanium dioxide used as an emissivity agent orenhancer is obtained from a titanium dioxide containing waste streamfrom a polyolefin polymerization process.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

In the drawings, identical reference numbers identify similar elements.The sizes and relative positions of elements in the drawings are notnecessarily drawn to scale. For example, the shapes of various elementsand angles are not drawn to scale, and some of these elements arearbitrarily enlarged and positioned to improve drawing legibility.Further, the particular shapes of the elements as drawn are not intendedto convey any information regarding the actual shape of the particularelements, and they have been solely selected for ease of recognition inthe drawings.

Embodiments of the present disclosure are described hereinafter withreference to the Figures, in which:

FIG. 1 is a flowchart of a process for extracting or obtaining TiO₂ frompolyolefin catalyst waste that is to be used in preparing a highemissivity coating composition according to an embodiment of thedisclosure;

FIG. 2 is a flowchart of a process for preparing or producing a highemissivity coating composition according to an embodiment of thedisclosure;

FIG. 3 is a flowchart of a process for applying a high emissivitycoating composition to a substrate according to an embodiment of thedisclosure;

FIGS. 4A-4C are photos of cross sections of coating compositions appliedto a substrate after being subjected to simulated decoking conditions;and

FIGS. 5A-5C are photos of internal wall surfaces of a high temperaturefurnace coated with a commercially available SiC containing coatingcomposition after operating in the 1000° C. temperature range.

DETAILED DESCRIPTION

It will be appreciated that, although specific embodiments of thepresent disclosure have been described herein for purposes ofillustration, various modifications may be made without departing fromthe spirit and scope of the disclosure. Accordingly, the disclosure isnot limited except as by the appended claims.

In the following description, certain specific details are set forth inorder to provide a thorough understanding of various aspects of thedisclosed subject matter. However, the disclosed subject matter may bepracticed without these specific details. In some instances, well-knownstructures and methods of mixing ceramic precursors, recovering titaniumdioxide, and applying high emissivity coatings to substrates comprisingembodiments of the subject matter disclosed herein have not beendescribed in detail to avoid obscuring the descriptions of other aspectsof the present disclosure.

Unless the context requires otherwise, throughout the specification andclaims that follow, the word “comprise” and variations thereof, such as“comprises” and “comprising” are to be construed in an open, inclusivesense, that is, as “including, but not limited to.”

Reference throughout the specification to “one embodiment” or “anembodiment” means that a particular feature, structure, orcharacteristic described in connection with the embodiment is includedin at least one embodiment. Thus, the appearance of the phrases “in oneembodiment” or “in an embodiment” in various places throughout thespecification are not necessarily all referring to the same aspect.Furthermore, the particular features, structures, or characteristics maybe combined in any suitable manner in one or more aspects of the presentdisclosure.

Embodiments of the present disclosure are directed to high emissivitycoating compositions in which titanium dioxide (TiO₂) is used as anemissivity enhancing agent, in contrast to prior high emissivity coatingcompositions in which TiO₂ has been simply used as a filler. However,under high temperature conditions, the present inventors have observedthat TiO₂ exhibits emissivity enhancing properties due to a temperatureinduced TiO₂ microstructure transformation. TiO₂ has three naturalforms: anatase, rutile, and brookite. Anatase is mainly used forphotocatalytic application due to its UV absorption properties. Anataseis transformed to produce rutile at temperatures above 700° C. andrutile is commonly used in pigment, cosmetic and ceramic industries.Rutile is stable at high temperature and has been observed by thepresent inventors to be a good energy emissivity agent. Brookite hasless utilization due to its limited availability.

The use of TiO₂ in prior coating compositions as a filler has typicallyadversely affected coating composition price due to high TiO₂ cost.Embodiments of the present disclosure provide a coating compositioncomprising TiO₂ as an emissivity agent or an emissivity enhancer whereinthe TiO₂ is obtained in a cost-effective manner without comprisingoverall function or characteristics of the TiO₂ in the coatingcomposition. Particular embodiments of the present disclosure providecoating compositions containing TiO₂, in which the TiO₂ is obtained froman industrial waste source, for instance, a waste stream associated withthe production of a polyolefin catalyst. Obtaining TiO₂ from such typesof waste sources results in lower costs for the TiO₂, which improves theeconomic aspects of producing high emissivity coating compositions thatinclude such TiO₂. A process, method, or technique for obtaining TiO₂from an industrial waste source is detailed below in relation to aspectsof a high emissivity coating composition manufacturing process.

As will be described in more detail below, a high emissivity coating,coating system or coating composition according to the presentdisclosure is referred to herein as a “coating composition.” Inaddition, unless otherwise stated, all percentages (%) are percentweight-by-weight, also expressed as % by weight, % (w/w), wt % or simply%. The term “wet admixture” refers to the relative weight percentages ofthe constituents or components of a coating composition in solution orwith respect to a solution, and the term “dry admixture” refers to therelative percentages of the constituents or components of the drycoating composition separate from or prior to the addition of water andany liquid state reagents. A person of ordinary skill in the art willunderstand the manner in which wet admixture and dry admixture weightpercentages are related or convertible.

In the context of the present disclosure, the term “set” is defined as anon-empty finite organization of elements that mathematically exhibits acardinality (number of elements of a set) of at least 1 (i.e., a set asdefined herein can correspond to a singlet or single element set, or amultiple element set), in accordance with known mathematical definitions(for instance, in a manner corresponding to that described in AnIntroduction to Mathematical Reasoning: Numbers, Sets, and Functions,“Chapter 11: Properties of Finite Sets” (e.g., as indicated on p. 140),by Peter J. Eccles, Cambridge University Press (1998)).

Coating compositions in accordance with the present disclosure include(in a wet admixture) (1) approximately 2% to 60% by weight of a set orgroup of fillers, which excludes TiO₂; (2) approximately 5% to 70% byweight of a set or group of emissivity agents or emissivity enhancers,which includes TiO₂, and which can further include silicon carbide (SiC)and/or chromium oxide (Cr₂O₃), (3) approximately 5% to 20% by weight ofa set or group of matrix strength enhancers, and (4) approximately 2% to30% by weight of a set or group of binders.

Fillers as used in the present disclosure are materials that are addedto other materials to lower the consumption of more expensive componentsin high emissivity coating compositions. Fillers useful in the presentdisclosure include, but are not limited to, aluminum oxide (Al₂O₃),silicon dioxide (SiO₂), magnesium oxide (MgO), calcium oxide (CaO), andboron oxide (B₂O₃).

As used in the present disclosure, emissivity agents or emissivityenhancers are materials that increase the emissivity of high emissivitycoating compositions to which the emissivity agent or enhancer is added.Suitable emissivity agents or emissivity enhancers include, but are notlimited to, titanium dioxide (TiO₂), silicon carbide (SiC), chromiumoxide (Cr₂O₃), silicon dioxide (SiO₂), iron oxide (Fe₂O₃), boronsilicide (B₄Si), boron carbide (B₄C), silicon tetraboride (SiB₄),molybdenum disilicide (MoSi₂), tungsten disilicide (WSi₂), and zirconiumdiboride (ZrB₂).

As used in the present disclosure, matrix strength enhancers or thermalstrength enhancers are materials that increase the resistance to stressand thermal stress of high emissivity coating compositions that includesuch matrix strength or thermal strength enhancers. In variousembodiments, useful matrix strength enhancers or thermal strengthenhancers include, but are not limited to, ceramic borides, ceramiccarbides, and/or ceramic nitrides (e.g., Ultra High Temperature Ceramics(UHTCs), which exhibit high melting point, substantial chemicalinertness, and relatively good oxidation resistance in extreme thermalenvironments. In particular embodiments, matrix strength enhancersinclude, but are not limited to silicon carbide (SiC), hafnium diboride(HfB₂), hafnium carbide (HfC), hafnium nitride (HfN), tantalum diboride(TaB₂), tantalum carbide (TaC), tantalum nitride (TaN), titaniumdiboride (TiB₂), titanium carbide (TiC), titanium nitride (TiN),zirconium diboride (ZrB₂), zirconium carbide (ZrC), and zirconiumnitride (ZrN). Additionally, in certain embodiments, thermal strengthcan be enhanced by the inclusion of binders such as, but not limited to,phosphoric acid (H₃PO₄), a sodium aluminosilicate and/or a potassiumaluminosilicate to form, for instance, Al₂(H₂P2O₇), Al(PO₃)₃, AlPO₄,and/or KAlSi₃O₈. A specific example of a binder is an aqueous solutioncontaining phosphoric acid (H₃PO₄) and sodium silicate.

The present inventors observed that a constituent dependent tradeoff canexist between coating composition emissivity, adhesion to substrates,and temperature stability. In other words, adjustment of weightpercentages of particular constituents in a coating composition canresult in changes in emissivity, temperature stability, and adhesioncapability of the coating composition. In order to simultaneouslyenhance emissivity, coating adhesion or cohesion, and high temperaturethermal and chemical stability, some coating composition embodiments inaccordance with the present disclosure include or establish a particularweight percentage of TiO₂ relative to the weight percentages of one ormore other coating composition constituents, such as Al₂O₃. Forinstance, particular coating composition embodiments include at leastapproximately 8% to 10% TiO₂ by weight with respect to a wet admixture.Additionally or alternatively, coating composition embodiments inaccordance with the present disclosure can include less thanapproximately 20% to 22% TiO₂ by weight with respect to a wet admixture,where a weight percentage of Al₂O₃ can be established or adjusted basedupon the selection of a given TiO₂ weight percentage. In certainembodiments, the weight percentages of Al₂O₃ and TiO₂ can be varied oradjusted to achieve varying emissivity and matrix adhesion capability.In some embodiments, wet admixture weight percentages of TiO₂ and Al₂O₃can be selected as approximately 20% and 22%, respectively, especiallywhen the TiO₂ is recovered from a waste source of TiO₂. In embodimentswhere the TiO₂ is from commercial sources, wet admixture weightpercentages of TiO₂ and Al₂O₃ can be selected as approximately 18% and16%, respectively. In particular embodiments, wet admixture weightpercentages of TiO₂ and Al₂O₃ can be selected as approximately 10% and32%, respectively. In the three foregoing embodiments on a dry basis,SiC is present in an amount less than 30 wt %, less than about 20 wt %,between about 8 wt % and less than 30 wt %, and between about 8 wt % andabout 20 wt %. In a specific embodiment, the SiC content is about 14 wt% on a dry basis.

In some embodiments, use of a set or group of matrix strength enhancersimproves the strength as well as the adhesion within a matrix of acoating composition. More particularly, matrix strength enhancerspossess an ability to decompose at working or operating temperatures toform or create new, altered, or reformulated matrices with other coatingcomposition constituents such as fillers. Such matrix strength enhancerscan include one or more ceramic borides, ceramic carbides, or ceramicnitrides. In multiple embodiments, SiC acts as a matrix strengthenhancer that can decompose to SiO₂ and CO₂ at temperatures above about400° C. and form a new matrix with aluminum oxide and silicon dioxide(Al₂O₃—SiO₂—SiC). The Al₂O₃—SiO₂—SiC ceramic matrix helps to enhancemechanical strength, i.e., bonding strength between particles in thecoating. More Al₂O₃—SiO₂—SiC matrixes are generated when more SiC ispresent in the coating. The inventors observed that the generatedAl₂O₃—SiO₂—SiC matrixes can increase the strength of the originalmatrix; however, it was also observed that too many Al₂O₃—SiO₂—SiCmatrices can result in defects in the matrix. At certain levels of SiCcontent in the coating composition, these matrix defects will bepredominant and cause reduced mechanical strength as evidenced byshrinkage of the coating composition. Such shrinkage can cause thecoating composition to crack and delaminate when the coating is adheredto the substrate to which it has been applied. Moreover, it was observedthat as more SiC decomposes to SiO₂ and more CO₂ is generated from thedecomposition reaction, more CO₂ tries to diffuse through the coatingcomposition. This CO₂ diffusion is evidence by small bubbles or voidsunderneath the surface of the coating composition. These small bubblesor voids can also lower mechanical strength of the coating compositionwhich results in shorter service life of the coating composition.

FIGS. 4A and 4B show photographs of cross sections of coatingcompositions in accordance with embodiments described herein applied toa substrate after being subjected to conditions simulating multipledecoking cycles in a naphtha cracking furnace (i.e., 22 cycles betweenroom temperature and holding at 1600° C. for one hour). In FIGS. 4A and4B no separation between the coating composition and the underlyingsubstrate is visible. FIG. 4C shows a photograph of a cross-section of acommercially available high emissivity coating composition applied to asubstrate and subjected to five of the same simulated decoking cycles asthe samples in FIGS. 4A and 4B. The sample in FIG. 4C shows a visiblecrack between the coating and the substrate, evidencing delaminationbetween the coating and the substrate.

Additionally or alternatively, in certain embodiments, matrix strengthenhancers can include one or more of hafnium diboride (HfB₂), hafniumcarbide (HfC), hafnium nitride (HfN), tantalum diboride (TaB₂), tantalumcarbide (TaC), tantalum nitride (TaN), titanium diboride (TiB₂),titanium carbide (TiC), titanium nitride (TiN), zirconium diboride(ZrB₂), zirconium carbide (ZrC), and zirconium nitride (ZrN).

As stated above, coating compositions in accordance with the presentdisclosure can include one or more chemicals or substances that serve asbinders or binding agents. Such binders promote bonding between acoating composition and a substrate on which the coating composition isapplied. Furthermore, said binders facilitate or effectuate support forthe coating composition by promoting binding between molecules of thecoating, (e.g., between Al₂O₃ and Al₂O₃ molecules) which facilitatecreating a matrix structure of the coating composition matrix itself. Inmultiple embodiments, a binder is or includes an aqueous solutioncontaining H₃PO₄. In various embodiments depending upon the type ofsubstrate, the binder is or includes sodium silicate (Na₂SiO₃). Incertain embodiments, the binders facilitate or effectuate the support ofan Al₂O₃—SiO₂—SiC matrix.

One embodiment of a high emissivity coating composition in accordancewith the present disclosure includes a dry admixture of approximately2.8% to 75% Al₂O₃, approximately 13.9% to 27.8% TiO₂, approximately 8.3%to 25.0% SiC, approximately 4.2% to 11.1% chromium oxide Cr₂O₃, andapproximately 5.6% SiO₂, where each of the foregoing percentages areweight percentages. The corresponding coating composition in a solutionor slurry form (in a wet admixture) includes, on a weight percentagebasis, from approximately 2% to 54% Al₂O₃, approximately 10% to 40%TiO₂, approximately 6% to 18% SiC, approximately 3% to 8% Cr₂O₃,approximately 4% SiO₂, and from approximately 2% to 28% water containingH₃PO₄.

In addition to the foregoing, colorants can be included in the coatingcomposition to form colored coating compositions. Examples of colorantsinclude but are not limited to yellow cadmium, orange cadmium, redcadmium, deep orange cadmium, orange cadmium lithopone, and red cadmiumlithopone. A colorant range or dilution ratio can be obtained from thecolorant manufacturer's specifications. Stabilizers known to enhancehigh temperature strength in refractory applications can also beincorporated into the coating compositions as required. Examples ofstabilizers include but are not limited to bentonite, kaolin, magnesiumalumina silica clay, stabilized zirconium oxide, tabular alumina, andother ball clay stabilizers.

Aspects of High Emissivity Coating Composition Manufacturing Processes

Process Aspects for Extracting or Obtaining TiO₂ from a PolyolefinCatalyst Waste

FIG. 1 shows a flowchart of a process 100 for extracting or obtainingTiO₂ for use in preparing a high emissivity coating, coating system orcoating composition (hereinafter collectively referred to as a coatingcomposition) according to an embodiment of the present disclosure from awaste source, waste stream, or waste solution containing a polyolefincatalyst. As used herein, waste source, waste stream, and waste solutionare used interchangeably and include but are not limited to processstreams or process batches that include catalysts that have been used ina polymerization process, such as the polymerization of olefins toproduce polyolefins. Waste sources, waste streams and waste solutionsare not necessarily intended for disposal and include streams,solutions, and sources that contain the spent catalyst and can bereactivated for reuse.

In a first process portion 110, at least one source, stream, or solutionincluding TiO₂ and/or one or more Ti compounds or compositions in one ormore forms from which TiO₂ can be obtained or extracted, for example awaste source, stream, or solution that includes TiO₂ and/or one or moreTi compounds or compositions in one or more forms from which TiO₂ can beobtained or extracted, is provided or obtained.

In accordance with embodiments of the present disclosure, a wastesource, stream, or solution containing catalyst associated with apolyethylene polymerization process is provided. Such a catalystcontaining waste source, stream, or solution can include or carry TiO₂.In various embodiments, the catalyst containing waste source, stream, orsolution including TiO₂ can be obtained from processes involvingZiegler-Natta catalysts, for example processes associated withpreparation and use of Ziegler-Natta catalysts.

In certain embodiments, a catalyst containing waste source can beobtained from a process involving homo- or co-polymerization of otherolefins, including polypropylene, polybutene, polymethylpentene,polycycloolefins, polycritadiene, polyisopropene, amorphouspoly-alpha-olefins and polyacetylene. In various embodiments, a suitablecatalyst containing waste source, stream, or solution can additionallyor alternatively be obtained from other processes that utilize catalystsystems that include TiO₂-rich sources and/or Ti bearing sources fromwhich adequate or substantial amounts of TiO₂ can be obtained orextracted, and which involve a generally straightforward and/oreconomical extraction process.

In particular embodiments, a source, stream, or solution including TiO₂can be obtained from ilmenite-type ore (i.e., an ore-based TiO₂ source).For instance, the source, stream, or solution including TiO₂ can beobtained from ilmenite-type ore using a membrane based electrodialysisprocess (e.g., a membrane based electrodialysis process as described byU.S. Pat. No. 4,107,264) or an organophosphoric acid extraction process(e.g., for example an organophosphoric acid extraction process forimpurity removal as described by U.S. Pat. No. 4,168,297). In addition,or as an alternative, in specific embodiments, a source, stream, orsolution including TiO₂ provided in the first process portion 110 can beobtained via TiO₂ pigment production processes, for example a TiO₂pigment production process described in U.S. Pat. No. 5,094,834.

In a second process portion 120, a known quantity and concentration of abasic solution or material is introduced or added to the TiO₂ source(s)under consideration (e.g., catalyst containing waste and/or ore-basedTiO₂ source) to thereby adjust the pH value of the catalyst containingwaste source. In representative embodiments, the basic solution caninclude but are not limited to one of sodium hydroxide (NaOH) andammonium hydroxide (NH₄OH). For instance, adding NaOH can adjust the pHof a catalyst containing waste source, stream, or solution fromapproximately 1.0 to 9.0, or from approximately 2.0 to 8.0, or fromapproximately 2.0 to 7.0. The one or more other basic solutions used toadjust pH of the catalyst containing waste source, stream, or solutionpreferably do not react with TiO₂.

A third process portion 130 involves precipitating or separating TiO₂from the (pH adjusted) TiO₂ source(s) under consideration, for instancecatalyst containing waste and/or ore-based TiO₂ source. In multipleembodiments, the treated TiO₂ source is allowed to settle, facilitate,or effectuate precipitation of TiO₂. The time duration allowed for thesettling or precipitation, and hence complete separation, can beadjusted or selected as required to achieve the desired separation. Forinstance, the TiO₂ source can be allowed to settle for approximately 10hours, 12 hours, 15 hours, or more.

In a fourth process portion 140, the precipitated TiO₂ is recovered andextensively washed for impurity removal, including the removal of saltssuch as sodium chloride (NaCl). In several embodiments, the collectedprecipitated TiO₂ is washed with deionized water, for instance,approximately 3 to 6 times or more. Subsequent to washing, theprecipitated TiO₂ is thermally treated in the presence of oxygen tothermally decompose the TiO₂ to rutile and/or to remove volatilefractions. The thermal treatment process can be carried out attemperatures of approximately 900° C. to approximately 1100° C. Thetemperature of the thermal treatment can be adjusted and is typicallybelow the melting point of TiO₂, which is approximately 1660±10° C. Theduration of a calcination or thermal treatment process can beapproximately 4 hours, 5 hours, or longer (e.g., about 7 or more hours).

In a fifth process portion 150, the resultant TiO₂ is collected uponcompletion of the calcination reaction(s) or thermal treatmentprocess(es). The collected TiO₂ may be allowed to cool down and is thenground to an average particle size less than approximately 65-mesh. Itwill be understood by one of ordinary skill in the art that the TiO₂ canbe readily ground to other average particle sizes or equivalent US sieveseries or Tyler mesh sizes larger or smaller than 65-mesh.

Aspects of Processes for Preparing or Producing High Emissivity CoatingCompositions

FIG. 2 illustrates a flowchart of a process 200 for preparing orproducing a coating composition according to embodiments of the presentdisclosure.

In the embodiments described with reference to FIG. 2, the process 200for preparing or producing a coating composition occurs in a batch-wisemanner. It should be understood that embodiments of preparing coatingcompositions described herein are not limited batch-wise processes andcontinuous processes can be used. In a first process portion 210, amixing container or a mixing tank is provided. The mixing container isconfigured to facilitate the mixing and distribution of particles orcontent therein. A wide variety of mixing containers are known in theart. Generally, such mixing containers are equipped with at least someform of an impeller, stirrer, and/or baffles, and optionally furtherequipped with rotating blades.

In a second process portion 220, predetermined amounts of ceramicprecursors, emissivity agents or emissivity enhancers, and matrixstrength enhancers used for preparing a coating composition areintroduced into the mixing container. Such ceramic precursors include afiller selected from aluminum oxide (Al₂O₃), silicon dioxide (SiO₂),magnesium oxide (MgO), calcium oxide (CaO), and boron oxide (B₂O₃). Anexemplary emissivity agent or emissivity enhancer includes titaniumdioxide (TiO₂), and in some embodiments an additional emissivityenhancer is selected from silicon carbide (SiC), chromium oxide (Cr₂O₃),silicon dioxide (SiO₂), iron oxide (Fe₂O₃), boron silicide (B₄Si), boroncarbide (B₄C), silicon tetraboride (SiB₄), molybdenum disilicide(MoSi₂), tungsten disilicide (WSi₂), and zirconium diboride (ZrB₂).Examples of matrix strength enhancers include silicon carbide (SiC),hafnium diboride (HfB₂), hafnium carbide (HfC), hafnium nitride (MN),tantalum diboride (TaB₂), tantalum carbide (TaC), tantalum nitride(TaN), titanium diboride (TiB₂), titanium carbide (TiC), titaniumnitride (TiN), zirconium diboride (ZrB₂), zirconium carbide (ZrC), andzirconium nitride (ZrN). In multiple embodiments, the ceramicprecursors, emissivity agents or emissivity enhancers, and matrixstrength enhancers have a specific or predetermined average particlesize selected to ensure uniform mixing. For instance, the ceramicprecursors, emissivity agents or emissivity enhancers, and matrixstrength enhancers may have a particle size of approximately 65-mesh,approximately 200-mesh, or approximately 325-mesh.

In a third process portion 230, the coating composition components arestirred or blended in the mixing container in accordance with a set ofmixing parameters intended to produce a well mixed mixture substantiallyfree of residues larger than about 250 microns.

A fourth process portion 240 involves addition of at least one binderinto the mixing container. As previously described, a binder supports acoating composition matrix and aids in promoting bonding between thecoating composition and a substrate or surface on which the coatingcomposition is applied. Hence, the binder(s) are selected based upon thetype of substrate to which the coating composition is to be applied. Ina number of embodiments, when the substrate is selected from at leastone of silica insulating brick, ceramic fiber, ceramic module,refractory brick, plastic refractory, castable refractory, fiberlite,ceramic tiles, an array of fiber board, and refractory mortar, anaqueous solution containing phosphoric acid (H₃PO₄) can be used as abinder. The concentration of phosphoric acid can be chosen, forinstance, to range from approximately 10%, 15%, or 20% volume/volume. Inseveral embodiments, when the substrate is a metal, sodium silicate(Na₂SiO₃) is a suitable binder.

In a fifth process portion 250, subsequent to an addition of the binderinto the mixing container, the mixture content, which includes theceramic precursors and the binder, is stirred or agitated to achieveuniform binder dispersion evidenced by residues no larger than about 250microns.

In a sixth process portion 260, the resultant coating composition iscollected from the mixing container. The coating composition can betransferred to a bucket or individual container having a predefinedvolume for storing, containing, receiving, or holding the coatingcomposition.

Aspects of Processes for Applying a Coating Composition on a Substrate

FIG. 3 is a flowchart of a process for applying a coating composition ona substrate according to embodiments of the present disclosure.

In a first process portion 310, a substrate is provided. The substratecan be selected from at least one of silica insulating brick, ceramicfiber, ceramic module, refractory brick, plastic refractory, castablerefractory, refractory mortar, fiberlite, ceramic tiles, an array offiber board, and metal. The substrate can be an inner lining, structure,and/or part of a furnace (e.g., a cracking furnace), a fire heater,preheater, reformer, other refractory equipment in the field, ceramicautomotive parts, refractory aerospace parts, or marine parts that aresubjected to high temperature when in use.

In a second process portion 320, the substrate is prepared for coating.In particular embodiments, the substrate is cured, baked, or cleanedprior to coating. For instance, the substrate can be cured by heating toa desired temperature for a specific duration to remove moisture andchemicals. In some embodiments, the substrate is cleaned using a dustcollector to remove dust or particles that may adversely impact orinterfere with bonding between the substrate and the coatingcomposition.

In a third process portion 330, a coating composition in accordance withembodiments of the present disclosure is provided. The coatingcomposition can be prepared in a manner identical or analogous to thatdescribed herein, and can be in the form of slurry. Prior to using, ifnecessary, the coating composition is agitated to ensure completeparticle dispersion because particles or sediments in the coatingcomposition may settle during storage. A portable electric mixer can beused for stirring the coating composition prior to applying the coatingcomposition to a substrate in a field operation. It is understood thatother types of mixers or agitators or stirrers can also be used.

In a fourth process portion 340, the coating composition is applied tothe surface of the substrate in a controlled manner. The coatingcomposition can be applied to the surface of the substrate using methods(i.e., surface coating methods) known to a person skilled in therelevant art. Exemplary methods include application with a brush, blade,or sprayer.

In a fifth process portion 350, the coated substrate is subjected to adrying process. For instance, the coating on the substrate can beallowed to dry for approximately 1 to 3 days or more.

The following representative Examples 1 through 3 illustrate effects,functions, and/or properties of coating compositions of the typedescribed in the present disclosure. It will be understood by a personof ordinary skill in the art that the scope of the present disclosure isnot limited to the following representative examples.

EXAMPLES Example 1 Effect of Variation of TiO₂ Content on Emissivity ofCoating Compositions

This example illustrates the effect of TiO₂ content on the emissivity ofcoating compositions. Generally speaking, increasing the amount of TiO₂increases the emissivity and this increase in emissivity as a result ofincreasing TiO₂ content is more pronounced at 400° C. to 1000° C. andless pronounced at 1100° C. and 1200° C. and least pronounced at 1300°C. This suggests that as the temperature at which the emissivity valueis determined increases, the impact on the emissivity value ofincreasing the TiO₂ content decreases.

Experiments were conducted to study the effect of TiO₂ content onemissivity of a coating, composition when TiO₂ was used as an emissivityagent or an emissivity enhancer in preparing a coating composition inaccordance with the second process portion 220 in FIG. 2.

Five emissivity coating compositions (A), (B), (C), (D), and (E), wereprepared. After preparation of each of the coating compositions, theywere applied by spraying on specimens of insulating brick with defineddimensions. The spray coating of high emissivity coating composition wasperformed using a commercial spray gun. To achieve smooth and goodcoverage, the bulk density of the coating composition was controlled toabout 1.50-1.70 kg/L. A nozzle diameter of about 1-2 mm and pressure ofabout 4-5 bar were employed. The distance between nozzle and coatingsurface was maintained at about 50 cm. The insulating brick was20×20×2.5 cm and a coating rate of about 1.8 kg/m2 was used. The coatedsubstrates were heated in a high temperature furnace at 800° C. for 5 hrto cure the coating and then the coating was allowed to cool to ambienttemperature. The cooled coated substrates were tested to determine theiremissivity.

The emissivity was measured using a standard pyrometer. Each substratesample was heated to the indicated temperature, the temperature of thesubstrate was measured, and the emissivity value was adjusted to forcethe pyrometer to display the correct temperature. The emissivity valuesof each of the coating compositions (A) to (E) at temperatures rangingfrom approximately 400° C. to 1300° C. were measured. It is alsounderstood by a person having ordinary skill in the art that othermethods or techniques may be alternatively used to measure emissivityvalue so long as the same technique is used for each specimen.

Preparation of Coating Compositions (A) to (E)

Each coating composition (A) to (E) was prepared using predeterminedamounts of ceramic precursors and an emissivity enhancer. Ceramicprecursors used included aluminum oxide (Al₂O₃), silicon carbide (SiC),chromium oxide (Cr₂O₃), silicon dioxide (SiO₂). Titanium dioxide (TiO₂)was used as an emissivity enhancer. Unless stated otherwise, ceramicprecursors and titanium dioxide were derived from commercially availablesources. Ceramic precursors used for preparing each of coatingcompositions (A) to (E) had an average particle size less thanapproximately 325-mesh.

On a wet admixture basis, weight percentages of TiO₂ in each of finalcoating compositions (A) to (E) were varied between approximately 10%and 40%, while those of SiC, Cr₂O₃, and SiO₂ were held constant.Additionally, weight percentages of Al₂O₃ were varied in a decreasingmanner between approximately 42% and 2% relative to increasing weightpercentages of TiO₂ in order to evaluate the effect(s) of TiO₂ contenton emissivity when the amount of a filler is decreased and an amount ofTiO₂ is increased.

The content of ceramic precursors in each of coating compositions (A) to(E) was as follows:

Coating Composition (A)

Coating composition (A) included approximately 42% Al₂O₃, 0% TiO₂, 18%SiC, 8% Cr₂O₃, and 4% SiO₂ by weight.

Coating Composition (B)

Coating composition (B) included approximately 32% Al₂O₃, 10% TiO₂, 18%SiC, 8% Cr₂O₃, and 4% SiO₂ by weight.

Coating Composition (C)

Coating composition (C) included approximately 22% Al₂O₃, 20% TiO₂, 18%SiC, 8% of Cr₂O₃, and 4% SiO₂ by weight.

Coating Composition (D)

Coating composition (D) included approximately 12% Al₂O₃, 30% TiO₂, 18%SiC, 8% Cr₂O₃, and 4% SiO₂ by weight.

Coating Composition (E)

Coating composition (E) included approximately 2% Al₂O₃, 40% TiO₂, 18%SiC, 8% Cr₂O₃, and 4% SiO₂ by weight.

Predetermined amounts of the ceramic precursors and emissivity enhancingagent described above were introduced into and then stirred in a mixingtank that achieved uniform mixing as evidenced by the absence of residuelarger than about 250 microns. Subsequent to stirring, an aqueoussolution containing phosphoric acid (H₃PO₄) at approximately 17%volume/volume was introduced into the mixing tank as a binder. Morespecifically, approximately 28% by weight of the aqueous solutioncontaining 17% volume/volume of H₃PO₄ was added into the stirred mixtureto make up a total of 100% by weight. The resulting mixture was allowedto stir for several minutes and the coating compositions were obtainedtherefrom.

The coating compositions were applied to the substrates using thetechnique described above.

Results

As illustrated in Table 1, in coating compositions (A) to (E) increasingTiO₂ content resulted in increasing emissivity, where emissivityincreases were particularly evident at temperatures of approximately400° C. to 1000° C. More particularly, a weight percentage of TiO₂ ofapproximately 20% or greater resulted in emissivity values ofapproximately 0.98-0.99 at approximately 1000° C., compared to anemissivity value of approximately 0.93-0.96 in the absence of TiO₂. Ingeneral, the inclusion of TiO₂ in weight percentages of approximately20% or more led to an approximate 1% to 6% increase in emissivityvalues, depending upon temperature, relative to coating composition (A)which excluded TiO₂. It was observed that at every temperature, addingTiO₂ resulted in an increase or at least no decrease in emissivity.

It was noted that coating compositions (C), (D), and (E) produced thehighest emissivity values at the different temperatures. Such coatingcompositions included approximately 20% TiO₂ or more, and less thanapproximately 22% Al₂O₃. It was further noted that for temperatures ofapproximately 400° C. to 1100° C., a TiO₂ weight percentage of at leastapproximately 10% gave rise to a desirable emissivity increase, i.e.,0.03 and 0.01 emissivity units, respectively.

TABLE 1 Emissivity Coating Compositions/ Emissivity value (ε) atspecific temperatures (TiO2 wt %) 400° C. 500° C. 600° C. 700° C. 800°C. 900° C. 1000° C. 1100° C. 1200° C. 1300° C. A/0 wt % 0.96 0.96 0.960.96 0.96 0.95 0.93 0.86 0.84 0.81 B/10 wt % 0.97 0.97 0.97 0.97 0.970.97 0.96 0.88 0.84 0.81 C/20 wt % 0.98 0.98 0.98 0.98 0.98 0.98 0.980.87 0.86 0.81 D/30 wt % 0.99 0.99 0.99 0.99 0.99 0.99 0.99 0.88 0.850.83 E/40 wt % 0.99 0.99 0.99 0.99 0.99 0.99 0.99 0.89 0.87 0.82

One of ordinary skill in the art will understand that dry admixtureweight percentages of the composition constituents given above can becalculated, e.g., by normalizing the specified wet weight percentageswith respect to an overall 72% percent dry weight in view of theaddition of 28% by weight aqueous solution containing H₃PO₄ into themixing tank or container.

Example 2 Effect of Source of TiO₂ on Emissivity of Coating Compositions

This example shows that TiO₂ obtained from a catalyst containing wastestream provides the same emissivity values as a coating compositioncontaining TiO₂ from non-waste commercial sources.

Experiments were performed comparing the effect the source of TiO₂ usedas an emissivity agent or an emissivity enhancer had on the emissivityof a coating composition prepared in accordance with the second processportion 220 of FIG. 2.

Four emissivity coating compositions (A), (B), (C), and (D), wereprepared. After preparation of each of the coating compositions, thecoating compositions were applied using the same substrates andtechnique described Example 1 above. The emissivity values of each ofthe coating compositions (A) to (D) at temperatures ranging fromapproximately 400° C. to 1300° C. were then measured in a manneridentical to that described above in Example 1.

Preparation of Coating Compositions (A) to (D)

Each coating composition (A) to (D) was prepared using predeterminedamounts of ceramic precursors and an emissivity enhancer. Ceramicprecursors included aluminum oxide (Al₂O₃), silicon carbide (SiC),chromium oxide (Cr₂O₃), and silicon dioxide (SiO₂). Titanium dioxide(TiO₂) was used as an emissivity enhancer. Al₂O₃, SiC, Cr₂O₃, and SiO₂were obtained from the same commercial sources that provided the samematerials in Example 1. TiO₂ was obtained from the same commercialsource that provided the TiO₂ used in Example 1 or from a polyolefincatalyst containing waste source, stream, or solution such as thatdescribed above in relation to the process 100 of FIG. 1. The detailedprocess for obtaining TiO₂ from a polyolefin catalyst containing wastestream used in this example is described below. Ceramic precursors andthe emissivity enhancing agent used for preparing each of coatingcompositions (A) to (D) had an average particle size less thanapproximately 325-mesh.

On a wet admixture basis, weight percentages of TiO₂ in each of finalcoating compositions (A) and (B) were maintained at approximately 10%,and TiO₂ weight percentages of each of final coating compositions (C)and (D) were maintained at approximately 20%. In coating compositions(A) and (B) the weight percentages of Al₂O₃ were maintained atapproximately 32 wt %. The Al₂O₃ weight percentages for coatingcompositions (C) and (D) were maintained at approximately 22 wt %.Weight percentages of SiC, Cr₂O₃, and SiO₂ were held constant forcoating compositions (A) to (D). The content or amount of ceramicprecursors and the sources of TiO₂ in each of coating compositions (A)to (D) were as follows:

Coating Composition (A)

Coating composition (A) included approximately of 10% TiO₂, 32% Al₂O₃,18% SiC, 8% Cr₂O₃, and 4% SiO₂ by weight. TiO₂ was obtained from acommercial source.

Coating Composition (B)

Coating composition (B) included approximately 10% TiO₂, 32% Al₂O₃, 18%SiC, 8% Cr₂O₃, and 4% SiO₂ by weight. TiO₂ was obtained from apolyolefin catalyst containing waste stream extraction process.

Coating Composition (C)

Coating composition (C) included approximately 20% TiO₂, 22% Al₂O₃, 18%SiC, 8% Cr₂O₃, and 4% SiO₂ by weight. TiO₂ was obtained from acommercial source.

Coating Composition (D)

Coating composition (D) included approximately 20% TiO₂, 22% Al₂O₃, 18%SiC, 8% Cr₂O₃, and 4% SiO₂ by weight. TiO₂ was obtained from apolyolefin catalyst containing waste stream extraction process.

Extraction of TiO₂ from Polyolefin Catalyst Containing Waste Streams

The polyolefin catalyst containing waste stream used as a source of TiO₂in Example 2 was obtained from a polyethylene manufacturing process.

Polyethylene catalyst containing waste stream or effluent (hereafter “PEcatalyst waste”) was collected from a polyethylene manufacturingprocess. The pH of the PE catalyst waste was adjusted from approximately2.0 to 7.0 by introducing a solution containing sodium hydroxide (NaOH).Upon pH adjustment, TiO₂ and Al(OH)₂ precipitated out and the mixturewas allowed to settle overnight. The precipitated portion containingTiO₂ was extensively washed with demineralized water approximately 4-5times to remove salts such as sodium chloride (NaCl). The washed TiO₂was subsequently dried at approximately 500° C. overnight and calcinedat approximately 1000° C. for about 5 hours to remove volatile fractionsand ensure the TiO₂ was in its rutile form. The resulting TiO₂ wasground to an average particle size less than approximately 65-mesh.

The ceramic precursors and TiO₂ were introduced into and stirred in amixing tank. Subsequent to the stirring, an aqueous solution containingphosphoric acid (H₃PO₄) at approximately 17% volume/volume wasintroduced into the mixing tank to serve as a binder. More specifically,approximately 28% by weight of the aqueous solution containing 17%volume/volume of H₃PO₄ was added into the stirred ceramic precursors andTiO₂ to make up a total of 100% by weight. The resulting mixture wasstirred for several minutes and the coating compositions were obtainedtherefrom.

The mixture was applied to the same type of substrates using the sametechnique as described above in Example 1.

Results

Emissivity values for specimens carrying coating compositions (A) to (D)were determined in the same manner as described in Example 1. Resultsshowing the emissivity value of each of coating compositions (A) to (D)are provided in Table 2 below. Results show that, at an equal weightfraction of 10% TiO₂ and ceramic precursors used, coating composition(B) has an identical or essentially identical emissivity value attemperatures of approximately 1000° C. and 1300° C. and almost orapproximately identical emissivity value at temperatures ofapproximately 1100° C. and 1200° C. as coating composition (A). Inaddition, results also demonstrate that, at an equal weight fraction of20% TiO₂ and identical weight fractions of ceramic precursors, coatingcomposition (D) has an identical emissivity value at temperatures ofapproximately 1100° C. and an almost or approximately identicalemissivity value at temperatures of approximately 1000° C., 1200° C. and1300° C. as compared to coating composition (C). These results indicatethat coating compositions prepared using TiO₂ from a polyolefin catalystcontaining waste source as described in the present disclosure, whichfunctions as an emissivity agent or emissivity enhancer, possessidentical, essentially identical, approximately identical, or comparableemissivity values depending on the temperature at which emissivity ismeasured as compared to coating compositions prepared using TiO₂ from anon-waste commercial source.

TABLE 2 Emissivity Coating Compositions/ Emissivity value (ε) atspecific temperatures Wt % TiO₂ 400° C. 500° C. 600° C. 700° C. 800° C.900° C. 1000° C. 1100° C. 1200° C. 1300° C. A/10 wt % 0.96 0.96 0.960.96 0.96 0.96 0.96 0.88 0.84 0.81 B/10 wt % waste 0.97 0.97 0.97 0.970.97 0.97 0.96 0.86 0.85 0.81 C/20 wt % 0.98 0.98 0.98 0.98 0.98 0.980.98 0.87 0.86 0.81 D/20 wt % waste 0.99 0.99 0.99 0.99 0.99 0.99 0.990.87 0.84 0.82

One of ordinary skill in the art will understand that dry admixtureweight percentages of the composition constituents given above can becalculated, e.g., by normalizing the specified wet weight percentageswith respect to an overall 72% percent dry weight in view of theaddition of 28% by weight aqueous solution containing H₃PO₄ into themixing container.

Example 3 High Emissivity Coating Compositions Surface Adhesion Testing

Experiments were conducted to evaluate bonding between high emissivitycoating compositions according to the present disclosure and a substrateto which the coating compositions were applied.

In this example, two coating compositions were prepared as described inthe following paragraphs.

Preparation of Coating Compositions (A) and (B)

Coating compositions (A) and (B) were prepared using predeterminedamounts of ceramic precursors. Ceramic precursors included aluminumoxide (Al₂O₃), silicon carbide (SiC), chromium oxide (Cr₂O₃), silicondioxide (SiO₂). Titanium dioxide (TiO₂) was employed as an emissivityenhancer. Al₂O₃, SiC, Cr₂O₃, and SiO₂ were derived from commerciallyavailable sources, and exhibited an average particle size less thanapproximately 425-mesh. TiO₂ was obtained from recovered polyethylenecatalysts as described in Example 2, and had an average particle sizeless than approximately 65-mesh. The content of ceramic precursors incoating compositions (A) to (B) was as follows:

Coating Composition (A)

Coating composition (A) included approximately 32% Al₂O₃, 10% TiO₂, 18%SiC, 8% Cr₂O₃, and 4% SiO₂ by weight.

Coating Composition (B)

Coating composition (B) included approximately 22% Al₂O₃, 20% TiO₂, 18%SiC, 8% Cr₂O₃, and 4% SiO₂ by weight.

The ceramic precursors and TiO₂ were introduced into and stirred in amixing tank. Subsequent to stirring, an aqueous solution containingphosphoric acid (H₃PO₄) at approximately 17% volume/volume wasintroduced into the mixing tank to serve as a binder. More specifically,approximately 28% by weight of the aqueous solution containing 17%volume/volume of H₃PO₄ was added into the stirred ceramic precursors tomake up a total of 100% by weight. The resulting mixture was stirred at25 rpm for several minutes after which the coating compositions werecollected.

In this example, a silica insulating brick was used as a substrate.Prior to application of the coating composition, the substrate wascleaned using a dust collector. The coating composition was sprayed ontothe substrate in a controlled manner using a 2.5 millimeter spray gun.More particularly, the pressure of the spray gun was approximately 5-6bar, and the amount of coating applied was approximately 1-1.6 kg/m².

Prior to an adhesion test, the coated substrate was heated atapproximately 800° C. for approximately 5 hours. The heated substratewas then allowed to cool down to ambient temperature.

The adhesion test was designed to simulate a decoking cycle that occursin a naphtha cracking furnace. In naphtha cracking furnace operation,the furnace is heated to an operating temperature of approximately 1100°C., and there are typically 8 decoking cycles in one service year.During a decoking cycle, the furnace heated to an operating temperatureof approximately 1100° C. is allowed to cool to ambient temperature.After cooling to ambient temperature, the furnace is heated to theoperating temperature again to start a second cycle. Therefore, in orderto verify that an emissivity coating composition will have at least oneservice year under typical annual decoking conditions, the adhesion testwas performed by heating the coated substrate to approximately 1600° C.(which is approximately 45% higher than an actual operating temperatureof a naphtha cracking furnace) for about 5 hours, and then the heatedsubstrate was cooled down to ambient temperature to simulate onedecoking cycle. This simulated decoking cycle was repeated 8 times.Subsequent to completion of one decoking cycle, the coating on thesubstrate was observed for shrinkage and cracking. Optical microscopy,scanning electron microscopy, and/or another observation technique canbe used to evaluate aspects of surface and interfacial adhesion of thecoating composition to the substrate. In this example, the heating andcooling process, followed by optical observation, inspection andmeasurement of the coating and substrate to evaluate the condition ofthe coating composition surface and interfacial adhesion was repeated 8times. Photographs of cross-sections of an insulating brick to whichcoating compositions (A) and (B) were applied are presented in FIGS. 4Aand 4B.

Coating compositions (A) and (B) were subjected to two types of adhesiontests in accordance with ASTM Designation C1624-05 to assess the qualityof the adhesion between the coating and the substrate. The first testwas a pull-off test that utilizes a dolly adhered to the coating. In thepull-off test a force was applied to the dolly in a direction away fromthe surface to which the dolly is adhered. An example of a device usefulfor carrying out adhesion testing is a PosiTest® Pull Off AdhesionTester available from DeFelsko Corporation of Ogdensburg, N.Y. Thesecond test was a scratch test to evaluate mechanical failure modes inaccordance with ASTM C1624-05.

Results

As observed from optical observation, inspection and measurement of thecoating and substrate, both coating compositions (A) and (B) exhibitedgood adhesion on the silica insulating brick substrates. At a coatingthickness of 200 microns, a maximum load of 3000 psi did not pull offthe coating from the substrate. A coating thickness of 200 micronsexhibited an adhesion strength of 38 N when tested in accordance withthe scratch test. In addition, both coating compositions (A) and (B)withstood thermal shock through 8 cycles of heating and cooling.

FIG. 4C is an optical image of a commercially available high emissivitycoating composition sold under the brand name QZ by SZET having an SiCcontent of about 23 wt % on a wet basis. The commercially availablecoating delaminated from the substrate as evidenced by the crack betweenthe substrate and the coating. Such delamination becomes apparent onsurfaces that have been coated with high emissivity coatings that do notexhibit the same levels of substrate adhesion, thermal resistance, andmechanical properties as the coating compositions of the disclosedembodiments. FIGS. 5A-5C are photographs of the internal wall surface ofa naphtha cracking furnace coated with a commercially available highemissivity coating composition after three years of operation at 1200°C. The coating composition shown in FIGS. 5A-5C exhibited satisfactoryperformance during the first 3 months of operation during which a 3% to4% energy savings was observed; however, after the first three months,the performance dropped dramatically as evidenced by a drop in energysavings to about 0.5%. In addition, after three months in service somedelamination of the coating surface from the underlying substrate wasobserved. After three years of such operation, the coating shown inFIGS. 5A-5C had an SiC content of about 22% on a dry basis. Based onthis amount it is estimated that the coating composition as originallyapplied to the furnace walls contained about 30% to 40% SiC on a drybasis. In FIGS. 5A-5C, the coating is beginning to or has delaminatedfrom the underlying substrate due to the poor adhesion and thermalproperties of the commercially available coating. Without being bound toa theory, it is believed that the drop in performance as evidenced bythe delamination of the coating in FIGS. 5A-5C is a result of the SiCcontent or the original coating being 30% or more on a dry basis.

The results indicate that coating compositions (A) and (B) containingless than 30% SiC on a dry basis promote and maintain good adhesion tosilica insulating brick substrate and possess and maintain good thermalresistance under conditions simulating at least one service year of anaphtha cracking furnace. Unlike the commercially available coatingcomposition illustrated in FIG. 4C, coating compositions (A) and (B) didnot delaminate from their substrates after 8 simulated decoking cycles.Additionally, the results indicate that coating compositions inaccordance with the present disclosure that include a TiO₂ weightpercentage that falls within the TiO₂ weight percentage ranges spanningcoating compositions (A) and (B), plus or minus a weight percentagevariability of approximately 5% to 20% (e.g., about 10% to 15%) relativeto the extremes of this range and less than 30% on a dry basis of SiC,can provide both enhanced emissivity and desirable substrate adhesionproperties. For instance, coating compositions in accordance with thepresent disclosure having a wet admixture weight percentage of at leastapproximately 8% to 10% TiO₂; or a wet admixture weight percentage ofless than approximately 22% to 23% TiO₂, or a wet admixture weightpercentage between about 10% to 20% TiO₂, and an SiC content of lessthan 30% on a dry basis or even less than about 20% on a dry basisprovide enhanced emissivity and desirable substrate adhesion properties.In representative coating composition embodiments in accordance with thepresent disclosure, as a TiO₂ weight percentage is varied from oneparticular coating composition to another, the weight percentage of aparticular set of composition constituents (e.g., the weight percentageof Al₂O₃) can be adjusted accordingly, and the weight percentages ofother composition constituents can remain constant.

One of ordinary skill in the art will understand that dry admixtureweight percentages of the composition constituents given above can becalculated, e.g., by normalizing the specified wet weight percentageswith respect to an overall 72% percent dry weight in view of theaddition of 28% by weight aqueous solution containing H₃PO₄ into themixing container.

The results reported in Examples 1-3 were surprising and/or unexpected.Such results indicate that TiO₂ can act as an emissivity enhancer in athermal emissivity coating composition, and TiO₂ obtained from anindustrial waste source or stream, for instance, associated with apolyolefin polymerization process, can be used to produce a coatingcomposition having enhanced emissivity (e.g., an increase of 0.01 to0.06 emissivity units or more) as well as adhesion to substrateproperties that do not exhibit delamination over a substantial number ofthermal cycles and/or a long period of time. Furthermore, in particularembodiments, a coating composition that provides both enhancedemissivity and substrate adhesion properties in accordance withembodiments described herein need not include more than approximately30% SiC on a dry basis and 20% to 22% of TiO₂ (e.g., less thanapproximately 20% TiO₂), but at least about 8% to 10% TiO₂ to provideappropriate emissivity enhancement on a wet admixture basis.Correspondingly, a coating composition in accordance with particularembodiments of the disclosure need not include more than approximately30% SiC on a dry basis and 27% to 30% TiO2 (for instance, less thanapproximately 27% to 29% (e.g., less than about 28%) TiO₂), but at leastabout 11% TiO₂ to provide appropriate emissivity enhancement on a dryadmixture basis. In certain embodiments, a coating composition inaccordance with embodiments of the disclosure can include less than 30%SiC on a dry basis and between approximately 8% to 16% TiO₂ on a wetadmixture basis, or between approximately 11% to 22% TiO₂ on a dryadmixture basis.

Representative examples of coating compositions provided by the presentdisclosure are described in Examples 4-6 below. It will be understood bya person of ordinary skill in the art that the scope of the presentdisclosure is not limited to the following compositions.

Example 4

A coating composition in the form of a slurry admixture was prepared inaccordance with the present disclosure. The composition includedapproximately 22% by weight of aluminum oxide (Al₂O₃), approximately 18%by weight of silicon carbide (SiC), approximately 8% by weight ofchromium oxide (Cr₂O₃), approximately 4% by weight of silicon dioxide(SiO₂), approximately 20% by weight of titanium dioxide (TiO₂), andapproximately 28% by weight of water containing approximately 17%volume/volume of H₃PO₄. TiO₂ was selected from a commercial source, or atreated polyolefin catalyst waste stream as described in Example 2above, or a mixture of the two sources. TiO₂ from commercial sources hashigher purity than TiO₂ recovered from waste streams. For example, TiO₂from commercial sources exhibits purities of more than 99%, while TiO₂from waste sources has purity of 80% to 90% owing to the presence ofAl(OH)₃ that can be converted to Al₂O₃ in accordance with embodimentsdescribed previously above.

The coating composition was formulated using the process 200 of FIG. 2.

The coating composition had a density of approximately 1.5-1.6 kg/liter,emissivity higher than approximately 0.97 at approximately 1000° C.,emissivity (when measured in accordance with the description inExample 1) higher than approximately 0.85 at approximately 1200° C., andexhibited good surface adhesion to the coated substrate based on opticalobservations. The coating composition was applied directly to asubstrate using a spray gun. Due to its improved emissivity and adhesioncapability, a furnace including surfaces coated with the coatingcomposition described in this example would have its fuel gasconsumption desirably decreased by approximately 4% or approximately100-200 kilograms of fuel gas/hour at a furnace throughput ofapproximately 30-32 tons/hour. The calculated decrease in fuelconsumption is based on a cracking furnace with naphtha feed throughputof approximately 30-32 tons/hour and a normal fuel consumption ofapproximately 5 tons/hour of fuel gas. After applying the coating ofthis example, the fuel gas consumption of the furnace decreased byapproximately 100-200 kilograms/hour or about 2% to 4%. This fuel gassaving remained constant after 10 iterations of a decoking cycle.

Example 5

A coating composition in the form of a dry admixture was prepared inaccordance with the present disclosure. The composition includedapproximately 30.5% by weight of aluminum oxide (Al₂O₃), approximately25.0% by weight of silicon carbide (SiC), approximately 11.1% by weightof chromium oxide (Cr₂O₃), approximately 5.6% by weight of silicondioxide (SiO₂), and approximately 27.8% by weight of titanium dioxide(TiO₂). TiO₂ was selected from a commercial source, or a treatedpolyolefin catalyst waste stream as described in Example 2, or a mixtureof commercial and waste sources. TiO₂ from commercial sources has higherpurity than TiO₂ recovered from waste streams. For example, TiO₂ fromcommercial sources exhibits purities of more than 99%, while TiO₂ fromwaste sources has purity of 80% to 90% owing to the presence of Al(OH)₃that can be converted to Al₂O₃ in accordance with embodiments describedpreviously above.

The coating composition was prepared using process 200 of FIG. 2;however, process portion 240 was omitted. Ceramic precursors, namelyAl₂O₃, SiC, Cr₂O₃, SiO₂, and emissivity enhancing TiO₂ from commercialsources, had an average particle size less than approximately 325-mesh,while TiO₂ from a polyolefin catalyst containing waste stream treated inaccordance with Example 2 had an average particle size less thanapproximately 65-mesh.

The coating composition in the form of a dry admixture was prepared forease of shipping and storage. Prior to coating a substrate, the drycoating admixture was thoroughly mixed with phosphoric acid at aconcentration of 17% by volume in water in a controlled manner (e.g.,depending upon a mixer configuration) to prevent powders or particles ofceramic precursors from clumping and attaching to the side of the mixingcontainer.

The prepared coating was applied to insulating bricks forming the innerlining of a furnace. This furnace originally consumed approximately 1.25ton/hour of fuel gas when operating at approximately 450° C. The coatinghad emissivity 0.98 when the coated furnace operated at 450° C. and thisled to approximately 4% or 50 kg/hour of fuel gas consumption.

Example 6

A coating composition in the form of a slurry admixture was prepared inaccordance with the present disclosure. The composition includedapproximately 2% by weight of aluminum oxide (Al₂O₃), approximately 18%by weight of silicon carbide (SiC), approximately 8% by weight ofchromium oxide (Cr₂O₃), approximately 4% by weight of silicon dioxide(SiO₂), approximately 40% by weight of titanium dioxide (TiO₂), andapproximately 28% by weight of water containing approximately 17%volume/volume of H₃PO₄. TiO₂ was selected from a commercial source, or atreated polyolefin catalyst waste stream as described in the foregoing,or a mixture of the two sources. TiO₂ from commercial sources has higherpurity than TiO₂ recovered from waste streams. For example, TiO2 fromcommercial sources exhibit purities of more than 99%, while TiO₂ fromwaste sources has purity of 80-90% owing to the presence of Al(OH)₃ thatcan be converted to Al₂O₃ in accordance with embodiments describedpreviously above.

The coating composition was prepared using process 200 in accordancewith FIG. 2.

The coating composition had a density of approximately 1.5-1.6 kg/liter,emissivity higher than approximately 0.98 at approximately 1000° C.,emissivity (measured in accordance with Example 1) higher thanapproximately 0.86 at approximately 1200° C., and possessed very goodsurface adhesion to the coated substrate. The coating composition wasapplied directly to an insulating brick substrate using a spray gun asdescribed above in Example 1. The coating composition contributed atleast approximately 20% heat loss reduction in a furnace when applied toexposed surfaces. The 20% reduction in heat loss was based ondetermining the temperature of the outside surface of the furnace beforeand after applying the coating composition and applying conventionalheat transfer principles to calculate the difference in heat loss due toconduction through the furnace wall and convection at the furnace wallsurface at the ambient conditions (e.g., room temperature and windspeed).

Example 7

To assess the adhesion and cohesion properties of high emissivitycoatings having the compositions set forth in Table 3 below to aninsulating brick substrate, a scratch-test method (ASTM C1624-05 (10))was conducted on compositions 1, 2, and 3. Generally, a scratch testmethod consists of the generation of scratches with a sphero-conicalstylus including a Rockwell C diamond tip or hard metal tip having acone angle of 120° and a tip radius of 200 μm by drawing the stylus at aconstant speed across a coating-substrate system to be tested. As thestylus is drawn across the coating substrate system, either a constantor progressive loading at a fixed rate is applied to the substrate bythe stylus. For progressive loading, the critical load (Lc) is definedas the smallest load at which a recognizable failure occurs.

The driving forces for coating damage in the scratch test are acombination of elastic-plastic indentation stresses, frictional stressesand residual internal stresses. In a lower load regime, these stressesresult in conformal or tensile cracking of the coating which stillremains fully adherent to the substrate. The onset of these stressesdefines a first critical load. In a higher load regime, another criticalload is defined and corresponds to the onset of coating detachment fromthe substrate by spalling, buckling or chipping.

In this example, three scratches were performed on each sample using aCSM Instruments SA Revetest Scratch Tester (RST). The RST is suited totest adhesion/cohesion strength of hard coatings on soft substrates aswell as soft coatings on hard substrates. A hard metal tip having a coneangle of 120° was used to perform the measurements. The test conditionsand parameters are listed in Table 3. After the measurements, eachsample was cleaned with a duster spray and the distance between thepoint of initial contact between the stylus and the location wheredelamination of the coating from the substrate occurred was measured.Using the force applied/distance curve, the load corresponding to thelocation where delamination occurred was determined. The load when thedelamination occurred for each sample is reported in Table 4 below.

Each coating composition was prepared using the technique described inExample 1 above. Each sample was prepared by applying the wet coatingcomposition to an insulating brick substrate as described in Example 3.Prior to scratch testing, the coating was fired at 1200° C. for 5 hours.The fired coating was 200 micrometers thick.

TABLE 3 Scratch test conditions and parameters Test Conditions Testatmosphere Air Temperature 24° C. Humidity 40% Test Parameters IndenterHard metal tip (120°) Loading type Progressive Scanning load 0.9NInitial load 0.9N Final load  60N Loading rate 38.2 N/min Scratch length20 mm Speed 40 mm/min

TABLE 4 Sample composition, coating properties, and loads atdelamination 1 2 3 Coating composition (Bold is wet mixture/ Italics isdry mixture) Calcined alumina 21 29.2 16 22.2 11 15.3 Silicon carbide 912.5 14 19.4 19 26.4 Chromic oxide 6  8.3 6  8.3 6  8.3 Quartzite 3  4.23  4.2 3  4.2 Titania 18 25.0 18 25.0 18 25.0 Phosphoric acid 15 20.8 1520.8 15 20.8 Water 28 0  28 0  28 0  Total 100 100   100 100   100 100  Coating information Substrate: HI 28 HI 28 HI 28 Insulating brickCoating thickness 200 200 200 (μm) Firing temperature 1,200 1,200 1,200(° C.) Firing time (hr) 5 5 5 Load at Delamination (N) 1 21.4 38.8 28.72 23.7 37.6 31.4 3 22.1 37.5 27.1 Average 22.4 38.0 29.1 Standarddeviation 1.0 0.6 1.8

The results reported in Table 4 indicate that the sample compositionsdelaminated from the substrate at loads ranging from 21.4 N to 38.8 N.These results are a representation of the adhesion of the samplecompositions to the insulating brick substrate.

Additional Aspects of Coating Composition Formulation, Preparation, orSelection

In accordance with some embodiments of the disclosure, a targetemissivity level for a coating composition under consideration, or ameasure of emissivity enhancement for a set or group of coatingcompositions, can be determined or estimated by referencing or accessingdata that specifies a manner in which varying a TiO₂ concentration(e.g., on a wet or dry admixture weight percentage basis) relative tothe concentrations of one or more other coating composition constituents(e.g., a filler such as Al₂O₃) affects or can be expected to affectemissivity. Such data can be stored in an electronic format (e.g., in atable or database) or non-electronic format. Additionally, such data canalso include or specify a manner in which varying a TiO₂ concentration(e.g., on a relative basis with respect to a filler) can be expected toaffect coating composition adhesion to one or more types of substratesacross a predetermined period of time, for instance, a significant orlong period of time such as at least 6 months, approximately 1 year, ormore than 1 year. Based upon such data, a coating composition thatprovides enhanced emissivity as a result of the inclusion of anappropriate amount of TiO₂, as well as desirable substrate adhesionproperties across an appropriate time period, can be identified,selected, and readily prepared.

Particular embodiments of the disclosure are described above foraddressing at least one of the previously indicated problems. Whilefeatures, functions, processes, process portions, advantages, andalternatives associated with certain embodiments have been describedwithin the context of those embodiments, other embodiments may alsoexhibit such advantages, and not all embodiments need necessarilyexhibit such advantages to fall within the scope of the disclosure. Itwill be appreciated that several of the above-disclosed features,functions, processes, process portions, advantages, and alternativesthereof, may be desirably combined into other different methods,processes, systems, or applications. The above-disclosed features,functions, processes, process portions, or alternatives thereof, as wellas various presently unforeseen or unanticipated alternatives,modifications, variations or improvements thereto that may besubsequently made by one of ordinary skill in the art, are encompassedby the following claims.

The various embodiments described above can be combined to providefurther embodiments. All of the U.S. patents, U.S. patent applicationpublications, U.S. patent applications, foreign patents, foreign patentapplications and non-patent publications referred to in thisspecification and/or listed in the Application Data Sheet areincorporated herein by reference, in their entirety. Aspects of theembodiments can be modified, if necessary to employ concepts of thevarious patents, applications and publications to provide yet furtherembodiments.

These and other changes can be made to the embodiments in light of theabove-detailed description. In general, in the following claims, theterms used should not be construed to limit the claims to the specificembodiments disclosed in the specification and the claims, but should beconstrued to include all possible embodiments along with the full scopeof equivalents to which such claims are entitled. Accordingly, theclaims are not limited by the disclosure.

1. A thermal emissivity coating composition comprising: a dry admixtureof a set of emissivity agents including titanium dioxide, wherein aweight percentage of the titanium dioxide is less than approximately 28%by weight of the coating composition and at least approximately 10% byweight of the coating composition; and a set of matrix strengthenhancers selected from at least one of ceramic borides, ceramiccarbides, and ceramic nitrides.
 2. The thermal emissivity coatingcomposition of claim 1, wherein the coating composition includesapproximately 11-22% by weight of titanium dioxide.
 3. The thermalemissivity coating composition of claim 1, wherein the coatingcomposition includes at least approximately 10% by weight of titaniumdioxide and an increased emissivity value at a temperature range ofbetween approximately 400° C. and 1300° C.
 4. The thermal emissivitycoating composition of claim 1, wherein the coating composition includesat least approximately 20% by weight of titanium dioxide and anemissivity value of at least approximately 0.95 at a temperature ofapproximately 1000° C.
 5. The thermal emissivity coating composition ofclaim 1, wherein the emissivity value of the coating composition at atemperature of approximately 1000° C. increases as the percentage byweight of titanium dioxide in the coating composition increases.
 6. Thethermal emissivity coating composition of claim 1, wherein the set ofemissivity agents includes in addition to titanium dioxide at least oneemissivity agent selected from the group consisting of silicon carbide,chromium oxide, silicon dioxide, iron oxide, boron silicide, boroncarbide, silicon tetraboride, molybdenum disilicide, tungstendisilicide, and zirconium diboride.
 7. The thermal emissivity coatingcomposition of claim 1, wherein the set of matrix strength enhancersincludes at least one matrix strength enhancer selected from the groupconsisting of silicon carbide, hafnium diboride, hafnium carbide,hafnium nitride, tantalum diboride, tantalum carbide, tantalum nitride,titanium diboride, titanium carbide, titanium nitride, zirconiumdiboride, zirconium carbide, and zirconium nitride.
 8. The thermalemissivity coating composition of claim 7, further comprising at leastone filler selected from the group consisting of aluminum oxide, silicondioxide, magnesium oxide, calcium oxide, and boron oxide.
 9. The thermalemissivity coating composition of claim 1, wherein the coatingcomposition further comprises a solution component, and wherein a weightpercentage of titanium dioxide in a wet admixture of the coatingcomposition is less than approximately 20% by weight and at leastapproximately 10% by weight.
 10. The thermal emissivity coatingcomposition of claim 1, wherein the weight percentage of titaniumdioxide in a wet admixture of the coating composition is betweenapproximately 8% to 16% by weight.
 11. The thermal emissivity coatingcomposition of claim 9, wherein the solution component comprises abinder.
 12. The thermal emissivity coating composition of claim 11wherein the binder comprises phosphoric acid and/or sodium silicate. 13.The thermal emissivity coating composition of claim 1, furthercomprising about 2% to about 60% by weight filler selected from aluminumoxide, silicon dioxide, magnesium oxide, calcium oxide and boron oxide.14. The thermal emissivity coating composition of claim 1, furthercomprising on a dry basis about 8% to less than 30% SiC on a weightbasis.
 15. The thermal emissivity coating composition of claim 14,comprising on a dry basis about 8% to about 20% SiC on a weight basis.16. A method of preparing a thermal emissivity coating composition for asubstrate, the method comprising: obtaining titanium dioxide; providinga set of emissivity agents including the titanium dioxide; providing aset of matrix strength enhancers that includes at least one matrixstrength enhancer selected from the group consisting of ceramic borides,ceramic carbides, and ceramic nitrides; providing a set of fillers, atleast one filler selected from the group consisting of aluminum oxide,silicon dioxide, magnesium oxide, calcium oxide, and boron oxide; andcombining the set of emissivity agents, the set of matrix strengthenhancers, and the set of fillers, wherein the at least one fillercomprises about 2 wt % to about 60 wt % on a wet basis of the coatingcomposition.
 17. The method of claim 16, wherein the titanium dioxide isobtained from at least one of an industrial waste source and anore-based source.
 18. The method of claim 17, wherein the industrialwaste source comprises a polyolefin polymerization process waste source.19. The method of claim 18, wherein the industrial waste sourcecomprises a Ziegler-Natta catalyst containing waste source.
 20. Themethod of claim 17, wherein obtaining titanium dioxide from theindustrial waste source comprises: adjusting pH of the industrial wastesource to between about 7.0 to about 9.0; and precipitating titaniumdioxide from the pH adjusted industrial waste source.
 21. The method ofclaim 20, wherein obtaining titanium dioxide from the industrial wastesource further comprises subjecting precipitated titanium dioxide to athermal decomposition process.
 22. The method of claim 16, wherein theset of emissivity agents includes in addition to titanium dioxide atleast one emissivity agent selected from the group consisting of siliconcarbide, chromium oxide, silicon dioxide, iron oxide, boron silicide,boron carbide, silicon tetraboride, molybdenum disilicide, tungstendisilicide, and zirconium diboride.
 23. The method of claim 16, whereinthe set of matrix strength enhancers includes at least one matrixstrength enhancer selected from the group consisting of silicon carbide,hafnium diboride, hafnium carbide, hafnium nitride, tantalum diboride,tantalum carbide, tantalum nitride, zirconium diboride, zirconiumcarbide, and zirconium nitride.
 24. The method of claim 16, wherein adry admixture of the coating composition includes less thanapproximately 28% by weight of titanium dioxide and at leastapproximately 10% by weight of titanium dioxide.
 25. The method of claim24, wherein the dry admixture of the coating composition includes lessthan approximately 22% by weight of titanium dioxide and at leastapproximately 10% by weight of titanium dioxide.
 26. The method of claim16, wherein a wet admixture of the coating composition includes lessthan approximately 20% by weight of titanium dioxide and at leastapproximately 10% by weight of titanium dioxide.
 27. The method of claim26, wherein a wet admixture of the coating composition includes lessthan approximately 16% by weight of titanium dioxide and at leastapproximately 8% by weight of titanium dioxide.
 28. The method of claim16, further comprising: increasing an emissivity value of the coatingcomposition by adjusting the percentage by weight of titanium dioxidepresent in the coating composition.
 29. The method of claim 28, whereinthe percentage by weight of titanium dioxide in the coating compositionon a wet basis is at least 20% and the coating composition has anemissivity value of at least approximately 0.95 at a temperature ofapproximately 1000° C.
 30. The method of claim 16, further comprising:providing at least one binder selected from the group consisting ofphosphoric acid and sodium silicate; and combining the at least onebinder with the set of emissivity agents, the set of matrix strengthenhancers, and the set of fillers to form the coating composition. 31.The method of claim 16, further comprising: providing a substrate havinga plurality of surfaces; and applying the coating composition to atleast one surface of the substrate.
 32. The method of claim 31, whereinthe substrate is selected from the group consisting of silica insulatingbrick, ceramic fiber, ceramic module, refractory brick, plasticrefractory, castable refractory, refractory mortar, fiberlite, ceramictiles, an array of fiber board, and metal.
 33. The method of claim 32,wherein the substrate comprises a portion of a furnace, a fire heater, aceramic automotive part, a refractory aerospace part, or a marine part.34. The method of claim 33, wherein the furnace comprises a crackingfurnace.
 35. The method of claim 16, wherein a wet admixture of thecoating composition contains about 2% to about 60% by weight filler. 36.The method of claim 16, further comprising providing on a dry basisabout 8% to less than 30% SiC on a weight basis.
 37. The method of claim36, comprising providing on a dry basis about 8% to about 20% SiC on aweight basis.
 38. A method for modifying thermal emissivity of asubstrate using a thermal emissivity coating composition, the methodcomprising: identifying a target emissivity level or a target emissivitymodification; determining a coating composition titanium dioxideconcentration expected to provide the target emissivity level or thetarget emissivity modification; determining a set of substrate adhesionproperties for the coating composition; determining a coatingcomposition SiC concentration expected to provide the determined set ofsubstrate adhesion properties; and providing a thermal emissivitycoating composition that includes the determined titanium dioxideconcentration and the determined SiC concentration.
 39. The method ofclaim 38, wherein providing a thermal emissivity coating compositionthat includes the determined titanium dioxide concentration comprisesextracting titanium dioxide from an industrial waste stream or anore-based titanium dioxide source.
 40. The method of claim 39, whereinthe industrial waste stream comprises a polyolefin polymerizationprocess waste source.
 41. The method of claim 40, wherein the polyolefinpolymerization process waste source comprises a Ziegler-Natta catalystcontaining waste source.
 42. The method of claim 41, wherein extractingtitanium dioxide from the industrial waste stream comprises: adjustingpH of the industrial waste stream to between about 7.0 to about 9.0; andprecipitating titanium dioxide from the pH adjusted industrial wastestream.
 43. The method of claim 38, wherein the determining a coatingcomposition SiC concentration further comprises selecting an SiCconcentration on a dry basis of about 8% to less than 30% on a weightbasis.
 44. The method of claim 43, wherein the SiC concentration on adry basis is about 8% to about 20% on a weight basis.